MCNP Help: 10 Particles Lost

In summary, "MCNP Help: 10 Particles Lost" addresses the issue of particle loss in the Monte Carlo N-Particle Transport Code (MCNP) simulations. It explains the potential reasons for the loss of particles, such as geometry errors, incorrect material definitions, or inadequate source definitions. The document provides troubleshooting tips and strategies to identify and resolve these issues, ensuring more accurate simulation results.
  • #1
Optimus_Crime
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Thread moved from the technical forums to the schoolwork forums
In my intro class, I am trying to design for radiation sources. Currently, I am trying to plot the flux from neutron and photon source locations progressively moving further and further away, however the code is not running and it says "geometry error: no cell found run terminated because 10 particles got lost."
 

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  • #2
Hi,
you are trying to calculate an F5 (and F15) at (0,0,0) where your neutrons are emitted. Try to remove this calculation point, like this :
F5:N 10 0 0 1
20 0 0 1
30 0 0 1
40 0 0 1
50 0 0 1
60 0 0 1
70 0 0 1
80 0 0 1
90 0 0 1
100 0 0 1
110 0 0 1
120 0 0 1
130 0 0 1
140 0 0 1
150 0 0 1
 

FAQ: MCNP Help: 10 Particles Lost

What does "10 Particles Lost" mean in MCNP?

"10 Particles Lost" in MCNP refers to a warning message indicating that ten particles were not tracked or were lost during a simulation. This can occur due to various reasons, such as particles escaping the defined geometry, being absorbed by materials, or encountering undefined interactions.

What are common reasons for particles being lost in MCNP simulations?

Common reasons for particles being lost in MCNP include: particles exiting the simulation boundaries, being absorbed by materials without a defined interaction, or encountering geometrical configurations that lead to undefined behavior. Additionally, incorrect input parameters or geometry definitions can also contribute to particle loss.

How can I troubleshoot the "10 Particles Lost" warning?

To troubleshoot the "10 Particles Lost" warning, check the following: ensure that your geometry is correctly defined and that all materials have appropriate interaction data. Review the simulation boundaries to confirm that particles are not exiting the defined region. Additionally, examine the source definition and particle types to ensure they are set up correctly.

Is losing particles during a simulation a serious issue?

Losing a small number of particles, such as ten, may not significantly impact the overall results of a simulation, especially in large-scale models. However, if particle loss is frequent or increases significantly, it may indicate underlying issues with the model that need to be addressed to ensure accurate results.

How can I prevent particle loss in future MCNP simulations?

To prevent particle loss in future MCNP simulations, ensure that your geometry is well-defined and that all materials are properly characterized with the necessary interaction data. Use appropriate boundary conditions and source definitions, and consider refining the mesh or geometry if particles frequently escape. Regularly review simulation output for warnings and adjust parameters accordingly.

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